Capturing planet-warming carbon dioxide and turning it into useful products, from plastics to jet fuel, could make climate action cheaper and become a good business - but market obstacles need to be overcome first, researchers said on Thursday.
Companies are already turning carbon dioxide captured at industrial plants into materials such as road aggregate and low-carbon cement, scientists said in a paper published in the journal Nature.
Eventually products could also be made from carbon dioxide captured directly from the air, as the costs of that technology fall, they added.
"There are a lot of weird and wacky ideas out there, and we're just scratching the surface," said Cameron Hepburn, a University of Oxford professor in environmental economics and a lead author of the study. But efforts to turn captured carbon into products are still largely small-scale because most countries have yet to put an economic value on eliminating climate-changing gases while some of the processes require a lot of energy, he told the Thomson Reuters Foundation.
Construction standards and other regulations also make creating markets for new products difficult, said Hepburn, also director of the Smith School of Enterprise and the Environment.
With emissions from burning fossil fuels and clearing forests continuing to rise, scientists now believe holding warming to 1.5 °C above pre-industrial times will require sucking some carbon back out of the atmosphere.
In a landmark 2018 report, they said keeping global temperature rise to that more ambitious of two limits adopted in the 2015 Paris Agreement would substantially cut risks linked to planetary warming, from water shortages to wilder weather.
Scientists say carbon dioxide captured from smoke-stacks or the air could be stored permanently underground, but investment and policy to make that happen on a large scale have been slow to emerge.
In Europe, "we're so far off trend it makes you wonder what we're doing", Andrew Cavanagh, an emissions storage expert at Scotland's University of Edinburgh, told a September conference.
Instead, turning some of the carbon into products with a market value could be another way to drive investment into carbon capture, economists say.
FERTILISER TO SKYSCRAPERS
The Nature study, which examined thousands of papers on technologies to remove and use carbon, including natural processes, to gauge their viability, predicted they could together remove between 1 and 10 gigatonnes of emissions a year.
Burning fossil fuels is currently emitting 37 gigatonnes of carbon dioxide a year, and scientists predict the world will need to remove somewhere between 100 and 1 000 gigatonnes of carbon in total this century, the study said.
The technologies assessed ranged from turning carbon dioxide into a feedstock for plastic or fertiliser production, to finding ways to build skyscrapers in fast-growing cities out of carbon-sequestering wood or even carbon-negative cement blocks.
Researchers estimate that about $90 trillion will need to be spent globally by 2030 to build and update infrastructure, particularly as the world becomes more urban and cities grow.
That could create major new markets for carbon-storing building materials, said Ella Adlen, a researcher at the Oxford Martin School and another lead author of the paper.
But attracting investment in many of the technologies remains challenging because of problems ranging from regulatory barriers to poor financial returns due to a low - or absent - price on carbon, Hepburn said.
Capturing carbon directly from the air can also take large amounts of energy, although fast-falling costs for renewables may eventually eliminate that problem, he said.
Finding just a few initial lucrative uses for captured carbon dioxide could help "prime the pump" for more, as business interests push governments to change policy, Hepburn said.
"We have this big oil and gas industry taking carbon out of the ground and putting it into the air," he said. "We need an industry almost as big in reverse, taking carbon out of the air."
Capturing and using carbon dioxide cannot be a substitute for switching away from fossil fuels to cleaner sources of energy, he emphasised, even though the oil and gas industry is "very interested" in the new technologies.
"We need to do both as fast as possible," he added.
The paper's authors differed on the prospects for the carbon removal technologies, Hepburn noted, with some highly doubtful most will succeed and others more optimistic.
John Beddington, a former chief scientific adviser to the British government who pushed for the study, warned "the risk of getting (carbon capture and use) wrong is quite high".
"But if you do it right... you are tackling one of the key barriers to change, which is the cost of (climate) action," he said.